Entropy Drives an Attached Water Molecule from the C- to N-Terminus on Protonated Proline
Results from infrared photodissociation (IRPD) spectroscopy and kinetics of singly hydrated, protonated proline indicate that the water molecule hydrogen bonds preferentially to the formally neutral carboxylic acid at low temperatures and at higher temperatures to the protonated N-terminus, which be...
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Veröffentlicht in: | Journal of the American Chemical Society 2010-10, Vol.132 (42), p.14733-14735 |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | Results from infrared photodissociation (IRPD) spectroscopy and kinetics of singly hydrated, protonated proline indicate that the water molecule hydrogen bonds preferentially to the formally neutral carboxylic acid at low temperatures and at higher temperatures to the protonated N-terminus, which bears the formal charge. Hydration isomer populations obtained from IRPD kinetic data as a function of temperature are used to generate a van’t Hoff plot that reveals that C-terminal binding is enthalpically favored by 4.2−6.4 kJ/mol, whereas N-terminal binding is entropically favored by 31−43 J/(mol K), consistent with a higher calculated barrier for water molecule rotation at the C-terminus. |
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ISSN: | 0002-7863 1520-5126 |
DOI: | 10.1021/ja106167d |